1. Field of the Invention
The present invention relates to a flange-back adjustment method of a video camera, and particularly to an improved flange-back adjustment method of a video camera capable of advantageously reducing time needed for adjusting the flange-back and of correctly performing the flange-back adjustment.
2. Description of the Conventional Art
Referring to FIG. 1, there is shown a block diagram of a conventional video camera. As shown therein, the conventional video camera includes a lens section 10, a charge-coupled device (CCD) 20 for converting a light image from an object into electrical signals, a signal processing circuit 30 for processing the output signal of the CCD and for outputting a luminance signal Y and a chrominance signal C, a high pass filter 40 for filtering the luminance signal Y outputted from the video signal processing circuit 30, a signal detection circuit 50 for detecting the signal filtered via the high pass filter 40, a microcomputer 60 for outputting control signals in order to control zooming and focusing operations of the lens section 10 in accordance with the output signal of the signal detection circuit 50, and first and second motors M1 and M2 for providing the zooming and focusing operations of the lens section 10 with driving force in accordance with the control signals of the microcomputer 60.
Here, the lens section 10 includes a front lens 11, a movable variator lens 12 for performing the zooming operation, an iris 13 for passing a predetermined quantity of light, an intermediate lens 14, a movable focus lens is for performing the focussing operation, and first and second photo-interrupters 16 and 17 for respectively detecting the position of the variator lens 12 and the focus lens 15 and for transferring the detected position signal to the microcomputer 60.
The detailed operation of the conventional video camera will now be explained with reference to FIG. 1.
When light from an object is passed through the from lens 11 of the lens section 10, the variator lens 12 is moved for a proper zooming operation by the driving force generated from the first motor M1. Thereafter, the iris 13 controls the quantity of light passed from the variator lens 12. The light, the quantity of which is controlled therein, passes to the focus lens 15 through the intermediate lens 14. Here, the focus lens 15 is moved to a predetermined position so that the focussing of the object image is correctly performed as the variator lens 12 is moved.
The first and second photo-interrupters 16 and 17 detect the respective positions of the variator lens 12 and the focus lens 15 and transfer the signal corresponding to the detected position to the microcomputer 60.
The CCD 20 converts the light passed from the lens section 10 into electrical signals and then outputs the signals to the video signal processing circuit 30. The video signal processing circuit 30 processes the signals applied thereto and then outputs the chrominance signal C and the luminance signal Y. The high pass filter 40 receives the luminance signal Y outputted from the video signal processing circuit 30 and filters out the low band components of the luminance signal Y and then outputs the high band luminance signal to the signal detection circuit 50.
The signal detection circuit 50 detects the high band luminance signal and then outputs a result of such detection to the microcomputer 60. The microcomputer 60 judges the positions of the variator lens 12 and the focus lens 15 using the signals outputted from the first and second interrupters 16 and 17 and judges whether or not the focussing operation is correctly performed in accordance with the output signal of the signal detection circuit 50. Thereafter, the microcomputer 60 drives the first and second motors M1 and M2 to change the positions of the variator lens 12 and the focus lens 15, respectively.
However, the positions to which the focus lens 15 is moved in accordance with the changing positions of the variator lens 12 are determined at the time of designing the two lenses 12 and 15, and the data on the positions thereof is stored in the microcomputer 60 in the form of look-up tables.
Referring to FIG. 2, there are shown trace curves S1, S2, S3, and S4 which indicate every position of the focus lens 15 which is formed as the variator lens 12 is moved. As shown therein, as the variator lens 12 moves within a range from a wide-end limit to a tele-end limit, the focus lens 15 moves to predetermined positions in series along the trace curves S1, S2, S3 and S4, respectively.
In addition, if an object is not within a range of a predetermined distances(i.e., infinite, 10 m, 3 m, 1 m), the microcomputer 60 traces the trace curves S1, S2, S3, S4 and moves the focus lens 14 to a predetermined position.
However, the positions of the wide-angle end on each of the trace curves S1, S2, S3, S4 should be coincident with each other, but in actuality the positions thereof are not coincident with each other due to the manufacturing variance. Here, the variance is called "flange-back" which is usually used for compensating the trace curves S1, S2, S3, and S4, whereby the actual trace curve is obtained.
The conventional method of adjusting the flange-back will now be explained with reference to FIG. 3.
In the first step S1, the microcomputer 60 judges the position of the variator lens 12 in accordance with the signal from the first photo-interrupter 16 and drives the first motor M1 to move the variator lens 12 to a predetermined position of the wide-angle end.
In the second step S2, the image signal of the object imaged by the lens section 10 is processed in series by each of elements 20 to 50 and the result of such processes is inputted into the microcomputer 60. Thereafter, the microcomputer 60 judges whether or not a focussing operation is performed and drives the second motor M2 in order to move the focus lens 15 until the focussing operation is properly performed. After the focused condition is attained, the microcomputer 60 stores the position of the focus lens 15.
In the third step S3, the microcomputer 60 computes a position difference of the focus lens 15 along the trace curve between the wide-end and tele-end and moves the focus lens 15 by the computed position difference by driving the second motor M2.
In the fourth step S4, the microcomputer 60 moves the variator lens 12 to the tele-end on the trace curve by driving the first motor M1 and performs a focussing operation as in the second step S2 and then stores the position of the variator lens 12 as an updated tele-end position.
In the fifth step S5, the microcomputer 60 computes a position difference of the variator lens 12 between the wide-end and tele-end on the trace curve and moves the variator lens 12 towards the wide-end by the computed position difference by driving the first motor M1.
In the sixth step S6, the microcomputer 60 performs a focussing operation and stores the position of the focus lens 15.
In the seventh step S7, the microcomputer 60 compares the positions of the focus lens 15 which are stored in the second step S2 and the sixth step S6 and judges whether or not the position difference is within a predetermined range.
If the position difference is within the predetermined range, the position difference becomes a flange-back and then the flange-back operation is completed. Therefore, the focussing operation is performed using the trace curve which is updated by the flange-back.
In addition, if the position difference is not within the predetermined range, the steps S3 to S7 are repeatedly performed.
A conventional method of using a varying point on the trace curve in order to reduce the time required for adjusting the flange-back will now be explained with reference to FIG. 4.
In the first step S1', the microcomputer 60 recognizes the position of the variator lens 12 using the signals supplied from the first photo interrupter 16 and moves the variator lens 12 to a varying point on the trace curve by driving the first motor M1.
In the second step S2', the microcomputer 60 performs a focussing operation as in the second step S2 of FIG. 3 and stores the position of the focus lens 15.
In the third step S3', the microcomputer computes a position difference of the focus lens 15 on the trace curve between the varying point and the tele-end and moves the focus lens 15 by the computed position difference by driving the second motor M2.
In the fourth step S4', the microcomputer 60 moves the variator lens 12 to the tele-end by driving the first motor M1 and then performs a focussing operation as in the second step S2' and stores the position of the variator lens 12.
In the fifth step S5', the microcomputer 60 computes a position difference of the variator lens 12 between a varying point of the previously stored trace curve and the tele-end and moves the variator lens 12 towards the wide-end by the computed position difference by driving the first motor M1.
In the sixth step S6, the microcomputer 60 performs a focussing operation as in the second step S2' and stores the position of the focus lens 15.
In the seventh step S7, the microcomputer 60 compares the positions of the focus lens 15 which are stored in the steps S2' and S6'. If the difference between the stored positions is within a predetermined range, the eighth step S8' is performed.
In the eighth step S8', the microcomputer 60 computes a position difference of the focus lens 15 between a varying point on the previously stored trace curve and the wide-end thereof and moves the focus lens 15 by the computed position difference.
In the ninth step S9', the microcomputer 60 computes a position difference of the variator lens 12 between a varying point on the previously stored trace curve and the wide-end thereof and moves the variator lens 12 toward the wide-end by the computed position difference. Here, the moved position is set as the wide-end and then the adjustment of the flange-back is completed.
Meanwhile, if the position difference computed at the seventh step S7' is not within a predetermined range, the steps S3' to S7' are repeatedly performed.
The conventional flange-back adjustment method is performed by repeatedly moving the variator lens and the focus lens between the wide-end and the tele-end, so that it entails much time for adjusting the flange-back. In particular, in an attempt to reduce the adjusting time using the varying point on the trace curve, it is generally difficult to compute a more correct varying point since the inclination of the curve is relatively low. In addition, in the case that the lenses 12 and 15 cannot be moved between the wide-end and the tele-end, the flange-back adjustment cannot be performed.